The complement system is responsible for initiating and amplifying the inflammatory response to microbial infection and other acute insults. Inappropriate activation of complement has been implicated in pathological situations. For instance, the complement system has been implicated in contributing to the pathogenesis of several acute and chronic conditions, including atherosclerosis, ischemia-reperfusion following acute myocardial infarction, Henoch-Schonlein purpura nephritis, immune complex vasculitis, rheumatoid arthritis, arteritis, aneurysm, stroke, cardiomyopathy, hemorrhagic shock, crush injury, multiple organ failure, hypovolemic shock and intestinal ischemia, transplant rejection, cardiac Surgery, PTCA, spontaneous abortion, neuronal injury, spinal cord injury, myasthenia gravis, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, Guillain Bane syndrome, Parkinson's disease, Alzheimer's disease, acute respiratory distress syndrome, asthma, chronic obstructive pulmonary disease, transfusion-related acute lung injury, acute lung injury, Goodpasture's disease, myocardial infarction, post-cardiopulmonary bypass inflammation, cardiopulmonary bypass, septic shock, transplant rejection, xeno transplantation, burn injury, systemic lupus erythematosus, membranous nephritis, Berger's disease, psoriasis, pemphigoid, dermatomyositis, anti-phospholipid syndrome, inflammatory bowel disease, hemodialysis, leukopheresis, plasmapheresis, heparin-induced extracorporeal membrane oxygenation LDL precipitation, extracorporeal membrane oxygenation, and macular degeneration.
Complement can be activated through three distinct enzymatic cascades, referred to as the “classical”, “Lectin/MBL”, and “alternative” pathways (CP, MBL, and AP respectively). These pathways are shown schematically in FIG. 1. The CP is usually triggered by antibody bound to a foreign pathogen. Thus, this pathway requires prior exposure to that pathogen for the generation of specific antibodies. There are three plasma proteins specifically involved in the CP: C1, C2, and C4. MBL is a variation of CP, and is activated by the presence Lectin/MASP-2 but the cascade is similar to the CP.
In contrast to the CP and MBL, the AP is spontaneously triggered by foreign surfaces (e.g., bacteria, yeast, damaged tissue) or other abnormal surfaces, such as the artificial surfaces of medical devices (e.g., the surface of a machine where blood is circulated). There are three plasma proteins specific to the AP: factors B, D, and P (properdin). All three pathways converge at C3 and share C3 to C5-9 proteins that are involved in the later stages of the activation cascades. Anaphylatoxins C3a and C5a are produced because of complement activation. The terminal complement complex known as C5b-9, also known as the membrane attack complex (MAC), is the terminal product of the pathway.
FIG. 2 illustrates a schematic of AP activation. As a result of C3 tick over, C3b is generated. In the schematic, assumption has been made that tick-over of C3 and cleavage of C3 generates the same activated C3b with the released C3a. Activated C3b binds properdin oligomers present in blood to generated (P)n (C3b)n complex. Factor B having higher affinity to properdin bound C3b makes the complex PC3bB, which is then cleaved by factor D to generate PC3bBb. This active convertase cleaves additional C3 to make C3b and release C3a. The same C3 convertase with additional C3b molecules forms C5 convertase. The C5 convertase or C3 convertase cleave C5 to make C5b and C5a. The C5b molecule inserts into the lipid bilayer and forms the nucleus for MAC deposition.
It is well accepted that the alternative pathway serves as the amplification loop of all three pathways. To block the amplification loop function, antibodies to all three AP specific proteins have been developed and tested. Factor P monoclonal antibodies have been developed that inhibit both complement pathways. Anti-factor D and B antibodies have also been developed. While anti-properdin monoclonal antibodies have been developed, these monoclonal antibodies inhibit both the classical pathway and the alternative pathway (U.S. Pat. No. 6,333,034).
Polyclonal antibodies developed against TSR5 show that TSR5 is involved in C3b binding and AP activation (Perdikoulis, M. V., U. Kishore, and K. B. Reid, Expression and characterisation of the thrombospondin type I repeats of human properdin, Biochim Biophys Acta, 2001. 1548(2): p. 265-77). While the inhibition of P binding and AP hemolysis was only 40-50%, these authors suggested that TSR5 is important for properdin function. As a comparison, polyclonal antibodies to TSR1 and TSR2 demonstrated lack of inhibition in both assays. This publication teaches that TSR1 and TSR2 are functionally not active.
A more recent study teaches that total inhibition of properdin binding to C3b is required for inhibition of the C3a, C5a, and MAC (U.S. Pat. No. 6,333,034). This invention teaches that such antibodies will inhibit the classical complement pathway directly by inhibiting the classical pathway C3 convertase activity. While the patent teaches use of extracorporeal circulation as a model system with whole human blood, these studies do not teach the effect of anti-properdin monoclonal antibodies on monocyte and platelet activation. Activated monocytes are known to release TNF and form conjugates with platelets. The invention does not teach whether anti-properdin monoclonal antibodies will inhibit activation of monocytes and platelets. One would predict that inhibition of anaphylatoxin formation should have positive effects on inhibition of cellular activation; however, it is possible that such antibodies will activate cells via non-specific mechanisms.
U.S. Patent Application Pub. No. 2006/0093599 teaches that inhibition of properdin binding to C3b is not essential for inhibition of C3b and C5b-9 formation. In the patent application, fully human monoclonal antibodies were used that inhibited properdin binding to C3b and inhibited C3a, C5a, and C5b-9 production in whole blood. Unfortunately, these fully human monoclonal antibodies activated platelets, caused leukocyte platelet aggregate formation, and aggregated properdin monomers into higher oligomeric structures rendering such antibodies useless for therapeutic applications. The patent application provides no evidence/data that supports the fully human monoclonal antibody inhibits oligomerization of the properdin monomer. Blood is known to contain dimmers, trimers and tetramers of properdin. No monomers have been reported. It is unclear how the fully human monoclonal of U.S. Patent Application Pub. No. 2006/0093599 prevents the oligomerization of properdin monomer. The invention appears to be hypothetical and not founded on facts. Moreover, it was observed that the monoclonal antibody of U.S. Patent Application Pub. No. 2006/0093599 actually enhanced oligomer formation possibly explaining the observed platelet activation observed in extracorporeal circulation.